Interference patterns have been observed for buckyballs, and superposition has been observed for MEMS springs consisting of many thousands of atoms. Electromagnetic interference effects can occur with radiation that has kilometer-long wavelengths. Similarly, quantum encryption and key exchange have been performed over many kilometers.

> there is no gravity in QM

The weakness(es) of any one particular theory doesn't in an way disprove that macroscopic objects follow the same rules that microscopic objects do.

Just because MySQL is bad doesn't mean that the relational model is false, or that databases are pointless.

Just because the current theories of GR and QM aren't easily extended to all regimes doesn't meant that there is some sort of hard boundary where the rules change. Our theories of the world don't affect how it works. The boundaries of our theories are not boundaries of the world.

You can't fall of the edge of the world because the maps only go so far...

> Just because the current theories of GR and QM aren't easily extended to all regimes doesn't meant that there is some sort of hard boundary where the rules change. Our theories of the world don't affect how it works. The boundaries of our theories are not boundaries of the world.

Yes, absolutely agreed. My point was simply that we don't know how QM extends to macroscopic objects, not that there must be some hard boundary (though we can't exclude the possibility that there exists some hard boundary at some level of energy, just as we know that the Standard Model doesn't describe matter at certain high energies).

Until we have some unification of GR and QM, we can't say for sure that QM describes the macroscopic world, just as we can't say that GR describes the behaviors of particles. Most likely we will at some point find such a model, and find out exactly how QM applies to large systems - perhaps with some limits to uncertainty, similarly to how c acts as a limit to speeds.

> just as we can't say that GR describes the behaviors of particles

Sure it does - gravitational lensing, etc.

I guess more precisely, GR can't predict the interactions between particles, only the interaction of particles with gravitational fields. But GR can't predict the behavior of two colliding electrons - it will make similar predictions to classical physics, not the Schroedinger equation.